<div id='alert_msg' style="position:absolute;top:50%;left:50%;z-index:999;border:1px solid #f96;width:120px;height:32px;line-height:32px;margin:0 0 0 -60px;background-color:#ffc;border-radius:5px;color:#666;display:none;"></div>

<script>
function alert_msg(msg){
    var msg_info = msg;
    var alert_msg = $('alert_msg');
    $(alert_msg).setStyle('display','none');
    $(alert_msg).setStyle('margin-left',-60);
    $(alert_msg).setStyle('opacity',1);

    var myEffect = new Fx.Morph(alert_msg, { duration: '2500', transition: Fx.Transitions.Sine.easeOut });
    var scrollTop = getScrollTop();
    var clientHeight = getClientHeight();
    var currTop = scrollTop+clientHeight/2;

    $(alert_msg).set('text',msg_info);
    $(alert_msg).setStyle('display','block');
    $(alert_msg).setStyle('top',currTop);
    myEffect.start({ 'margin-left': 60, 'opacity': 0});
}

function getScrollTop()
{
    var scrollTop=0;
    if(document.documentElement&&document.documentElement.scrollTop)
    {
        scrollTop=document.documentElement.scrollTop;
    }
    else if(document.body)
    {
        scrollTop=document.body.scrollTop;
    }
    return scrollTop;
}

function getClientHeight()
{
    var clientHeight=0;
    if(document.body.clientHeight&&document.documentElement.clientHeight)
    {
        var clientHeight = (document.body.clientHeight<document.documentElement.clientHeight)?document.body.clientHeight:document.documentElement.clientHeight;        
    }
    else
    {
        var clientHeight = (document.body.clientHeight>document.documentElement.clientHeight)?document.body.clientHeight:document.documentElement.clientHeight;    
    }
    return clientHeight;
}
</script>